More in Neutrino Physics

Oscillations aren't the only property of neutrinos that are being studied by current experiments.

Several groups are attempting to measure the absolute mass scale of the neutrinos (rather than the mass differences found in oscillations). The basic principle of these experiments is generally to very carefully measure the area near the endpoint of a β decay spectrum. The difference between the endpoint energy and the energy difference between the initial and final nuclei is the neutrino mass. In practice, this is extremely difficult.

Other experiments are attempting to determine whether neutrinos are Dirac or Majorana particles. This is generally done by searching for neutrinoless double beta decay (0νββ decay). There are certain isotopes where regular β decay is not allowed due to energy conservation, but simultaneous emission of two electrons is allowed, This leads to double β decay, although the half-lives of these isotopes are often very long so the decays may be difficult to find.

If neutrinos are Majorana particles, they are their own antiparticles. In normal double β decay, there are two electrons and two neutrinos in the final state in addition to the daughter nucleus. However, for Majorana neutrinos, it is also possible for the two neutrinos to merge, leaving no neutrinos in the final state. In this case, the energy is all carried by the electrons. While the two-neutrino case results in a wide β-like energy spectrum for the two electrons, in the zero-neutrino case, all the energy goes to the electrons so an energy peak is found at the endpoint energy of the two neutrino case. For Majorana neutrinos, both types (2- and 0-ν) of decays occur so the neutrinoless decays must be found on top of a potentially large background from 2-ν decays.